On August 30, Gennady Borisov, an amateur astronomer from Crimea, Ukraine, discovered a shiny object in the night sky with the 65-centimetre telescope he had built himself. The body was surrounded by a very compact cloud of dust and gas and also showed a tail, typical signs that it could be a comet,
Amateur and professional astronomers pointed their telescopes at the new object to try to clarify where they came from. On 24 September, the International Astronomical Union confirmed that it was an interstellar body arriving from somewhere outside the solar system. He was the second visitor of its kind to have been discovered, after 1I/Oumuamua, a missile-shaped asteroid that crossed the solar system in 2017.
The new body is named after its discoverer preceded by a figure that identifies it as the second known interstellar object: 2I/Borisov. It currently travels to the Sun at 32 kilometers per second, even faster than its predecessor,Amateur astronomer Gennady Borisov making one of his ESA/Borisov telescopes
After studying its orbit, a team of Polish astronomers suggests that the object comes from Kruger 60, a binary solar system made up of two red dwarf stars that is 13 light-years from Earth. Comet Borisov entered the solar system from above, on a plane almost perpendicular to Earth's orbits and other planets. On December 7, it will reach its closest point to the Sun, when it will be at an identical distance from the star and Earth: 299 million kilometers. A few days later, on January 4, the comet, visible only from the Earth's southern hemisphere, is expected to reach its peak of brightness. Then he'll move away until he gets out of the solar system,
On September 10, a team of astronomers in Poland and the Netherlands observed the comet with the Gemini North telescope in Hawaii and the William Herschel, located on the island of La Palma in the Canary Islands. His observations, published on Monday in Nature Astronomy, show that the comet's nucleus is one kilometer in diameter. Its gas casing is reddish, which suggests that its composition is so similar to that of native comets that it is "indistinguishable" from them, the study's authors say. Due to its orbit, Borisov's comet will be able to be studied in much more detail than Oumuamua before it leaves the solar system, in about a year,
"2I/Borisov has a hyperbolic orbit, whose eccentricity tells us that it does not come from our solar system," confirms Inés Pastor, a Segovian astronomer who works at the University of Amsterdam and is a co-author of the study. "We still have about a year before it is stopped, by September 2020. Because of its orbit, once it starts to move away from the sun, it will never visit the solar system again," he adds
these bodies are still a profound mystery to scientists, partly because two are barely known. Oumuamua, a Hawaiian explorer, was discovered on October 19 by the Hawaii Pan-STARRS telescope, which specializes in tracking parts of the sky already covered by other instruments to find differences and discover new objects. The body, a very elongated asteroid that aroused all sorts of unfounded speculations about its origin, could only be observed for a few days and its composition is still a mystery. Comet Borisov, the first one from outside the solar system, has fewer riddles. From now on it is thought that more interstellar travelers will be discovered thanks to the launch of the Large Tracking Telescope (LSST), which will start operating from Chile in three years.